Seung Jun Hwang

The design of electrocatalysts for polymer electrolyte membrane fuel cells must satsify two equally important fundamental principles: optimization of electrocatalytic activity and long-term stability in acid media (pH <1) at high potential (0.8 V). We report here a solution-based approach to the preparation of Pt-based alloy with early transition metals and realistic parameters for the stability and activity of Pt(3)M (M = Y, Zr, Ti, Ni, and Co) nanocatalysts for oxygen reduction reaction (ORR).

Halogen photoelimination reactions constitute the oxidative half-reaction of closed HX-splitting energy storage cycles. Here, we report high-yielding, endothermic Cl2 photoelimination chemistry from mononuclear Ni(III) complexes. On the basis of time-resolved spectroscopy and steady-state photocrystallography experiments, a mechanism involving ligand-assisted halogen elimination is proposed. Employing ancillary ligands to promote elimination offers a strategy to circumvent the inherently short-l

A new strategy for the synthesis of condensed hetero- or carbocycles such as pyrroloindoles or fluorenes has been developed that involves the Pd-catalyzed cyclization of readily available N-(2-halobenzyl)pyrroles or their phenyl derivatives. The reaction is proposed to proceed via oxidative addition of benzylic halides to Pd(0) followed by base-assisted C-H bond activation. A broad range of condensed cyclic products could be obtained in good to excellent yields under mild conditions.

Endothermic halogen elimination reactions, in which molecular halogen photoproducts are generated in the absence of chemical traps, are rare. Inspired by the proclivity of mononuclear Ni(III) complexes to participate in challenging bond-forming reactions in organometallic chemistry, we targeted Ni(III) trihalide complexes as platforms to explore halogen photoelimination. A suite of Ni(III) trihalide complexes supported by bidentate phosphine ligands has been synthesized and characterized. Multin

A facile protocol for the Pd-catalyzed preparative synthesis of fluorene derivatives has been developed. While a wide range of fluorenes were easily obtained with high efficiency and selectivity under mild conditions, excellent functional group tolerance was also demonstrated. On the basis of Hammett and KIE studies, the present reaction is proposed to proceed via a base-assisted deprotonative metalation pathway.

Core@shell electrocatalysts for fuel cells have the advantages of a high utilization of Pt and the modification of its electronic structures toward enhancement of the activities. In this study, we suggest both a theoretical background for the design of highly active and stable core@shell/C and a novel facile synthetic strategy for their preparation. Using density functional theory calculations guided by the oxygen adsorption energy and vacancy formation energy, Pd₃Cu₁@Pt/C was selected as the mo

A facile room temperature synthesis technique has been developed for Pt-Ir/C electrocatalysts for applications to low-temperature fuel cells. The prepared Pt(x)Ir(y) electrocatalyst was highly stable and active toward the oxygen reduction reaction (ORR), as well as liquid fuel oxidation reaction with high CO tolerance.

Abstract The catalytic activity of a wide range of copper salts, including Cu(I) and Cu(II), has been examined in the Cu-catalyzed three-component coupling reactions of sulfonyl azides, terminal alkynes, and amines, alcohols, or water to afford N -sulfonyl amidines, imidates, and amides, respectively. Furthermore, the investigation on the ligand effect in our protocol has revealed that certain types of ligands such as tris(benzyltriazolylmethyl)amine (TBTA) exhibited notable acceleration effects

Insertion of a tricoordinate phosphorus ligand into late metal-carbon bonds is reported. Metalation of a P^P-chelating ligand (<b>L1</b>), composed of a nontrigonal phosphorous (i.e., P(III)) triamide moiety, P(N(<i>o</i>-N(Ar)C₆H₄)₂, tethered by a phenylene linker to a -P<i>ⁱ</i>Pr₂ anchor, with group 10 complexes L₂M(Me)Cl (M = Ni, Pd) results in insertion of the nontrigonal phosphorus site into the metal-methyl bond. The stable

The challenge that short excited state lifetimes of first-row transition metal complexes present to the photoactivation of M–X bonds has been overcome with a phosphine mediator coupled to a nickel metal catalyst.

High Resolution Image Download MS PowerPoint Slide Electronic structure–reactivity relationships are fundamental to advancing the redox chemistry of main-group elements. Herein, we investigate a series of planarized C 2v pnictogen complexes (Pn = P, Sb, Bi) to correlate their electronic structures with reactivity trends across the pnictogen group. Through single-crystal X-ray diffraction, UV–vis spectroscopy, electrochemical measurements, and density functional theory (DFT) calculations, we demo

The reduction of dioxygen to water is crucial in biology and energy technologies, but it is challenging due to the inertness of triplet oxygen and complex mechanisms. Nature leverages high-spin transition metal complexes for this, whereas main-group compounds with their singlet state and limited redox capabilities exhibit subdued reactivity. We present a novel phosphorus complex capable of four-electron dioxygen reduction, facilitated by unique phosphorus-ligand redox cooperativity. Spectroscopi

Bimetallic complexes have sparked interest across various chemical disciplines, driving advancements in research. Recent advancements in this field have shed light on complex reactions in metalloenzymes and unveiled new chemical transformations. Two primary types of bimetallic platforms have emerged: (1) systems where both metals actively participate in reactivity, and (2) systems where one metal mediates the reaction while the other regulates reactivity. This study introduces a novel multinucle